Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Physical chemistry → Surface chemistry ↓


Colloids and Emulsions


Colloids and emulsions are important topics in the field of surface chemistry, which is an important branch of physical chemistry. Understanding these two concepts requires a deeper look into the complexities of mixtures and how different types of substances interact with one another. This lesson will explore colloids and emulsions in detail, aiming to explain these concepts in simple terms, supported by visual and textual examples.

Introduction to colloids

Colloids are mixtures where one substance is evenly dispersed throughout another substance. The particles in a colloid are typically larger than those in a true solution but smaller than those in a suspension. Their size ranges from about 1 nanometer to 1 micrometer.

Types of colloids

  • Sol: A solid substance dispersed in a liquid. Example: paint, dirty water.
  • Gel: A fluid dispersed in a solid substance. Examples: jelly, cheese.
  • Foam: A gas dispersed in a liquid. Examples: whipped cream, shaving cream.
  • Aerosol: A liquid or solid substance dispersed in a gas. Example: fog, smoke.
  • Emulsion: A liquid dispersed in another liquid. Examples: mayonnaise, milk.
oil droplets in water (emulsion)

Colloids play important roles in a variety of scientific and industrial fields, such as food, pharmaceuticals, and cosmetics. Their unique properties are a result of the size and interactions of their particles, which are so small that they can remain suspended and do not settle to the bottom like larger particles in suspension.

Properties of colloids

Colloids have unique properties that distinguish them from other types of mixtures and solutions. Some of these properties are:

  • Tyndall Effect: It is the scattering of light by colloidal particles. When a beam of light passes through a colloid, the path of the light becomes visible because the particles scatter the light. This is why we can see a ray of sunlight passing through a dusty room.
  • Brownian motion: The random and continuous motion of colloidal particles when suspended in a fluid. It is caused by collisions with molecules of the dispersion medium.
  • Electrophoresis: Movement of charged colloidal particles in an electric field. Positively charged particles move towards the cathode and negatively charged particles move towards the anode.
  • Absorption: Colloidal particles can absorb substances onto their surface, which makes them highly reactive and able to catalyze chemical reactions.
Light source Light scattering (Tyndall effect)

Stability of colloids

Colloids are relatively stable compared to suspensions, but their stability can change depending on various factors such as temperature, presence of electrolytes, and the nature of the dispersed phase and dispersion medium.

Stabilization methods

  • Electrostatic stabilization: Charged particles repel each other, preventing deposition.
  • Static immobilization: Large molecules adsorbed on the surface provide a physical barrier to deposition.
Positive Charge Positive Charge

Introduction to emulsions

An emulsion is a special type of colloid consisting of two immiscible liquids, one of which is dispersed within the other. Emulsions are classified based on the state of the dispersed and continuous phase.

Types of emulsions

  • Oil-in-water (O/W): Oil droplets are dispersed in water. Example: milk, mayonnaise.
  • Water-in-oil (W/O): Water droplets are dispersed in oil. Example: butter, margarine.

Emulsions are widely used in industries such as food production, pharmaceuticals, cosmetics, and painting.

Emulsifiers and emulsion stabilizers

Emulsions are inherently unstable, and they separate into their individual components over time. The stability of emulsions can be increased by adding substances called emulsifiers. Emulsifiers are surface-active agents that reduce the interfacial tension between two immiscible liquids and form a stable film around dispersed droplets.

For example, in making mayonnaise, which is an oil-in-water emulsion, egg yolk acts as an emulsifier. Egg yolk contains lecithin, which has hydrophilic and hydrophobic ends, which help stabilize the emulsion.

Emulsifier (lecithin) Oil Water

Applications of colloids and emulsions

Both colloids and emulsions have numerous applications in daily life and industrial processes:

  • Food industry: Many food products such as mayonnaise, ice cream and sauces are emulsions.
  • Medical field: Various drug delivery systems use colloidal carriers such as liposomes and nanoparticles to deliver active ingredients.
  • Cosmetics: Creams, lotions, and ointments often contain colloidal mixtures that improve the application and durability of cosmetic products.
  • Paints and coatings: Paints are often colloidal dispersions of pigments in a solvent; they provide a uniform and pigmented coating surface.
  • Water treatment: Colloidal particles can be removed using coagulants during water treatment processes.

Challenges in the study of colloids and emulsions

Studying colloids and emulsions is fraught with many challenges due to their complex nature. The main challenges include understanding the interactions at the nano- and microscale, controlling stability over time, and characterizing and measuring their properties.

Advances in analytical techniques such as electron microscopy and dynamic light scattering have helped researchers gain deeper insights into the behavior and properties of colloidal systems.

Conclusion

Colloids and emulsions are an essential aspect of surface chemistry and colloid science. Their unique properties and diverse applications highlight their relevance in various industrial and scientific fields. Understanding their formation, stability and properties is crucial for the development of new products and technologies. The ongoing study of colloidal systems remains a vibrant field of research, with constant developments in both theoretical and applied science.


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Colloids and Emulsions

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